Within the brain, cytomegalovirus (CMV) is the leading viral cause of congenital disease, often producing serious neurological deficits. By attacking the developing CNS, CMV causes serious brain disorders that include microencephaly, epilepsy, deafness, microgyria, mental retardation, sensory loss, motor problems, and psychiatric disturbances. CMV is also a clinically important opportunistic virus that can lead to serious neurological disease in AIDS patients. Despite the clinical importance of CMV infections of the brain, relatively little experimental work has been done in this area, and many basic questions remained unanswered. The present application addresses basic mechanisms of viral spread into and within the brain, and the repercussions of this infection. A recombinant mouse CMV expressing GFP will be used to identify infected cells and track virus dispersal. CMV shows rapid dispersal in developing but not mature brain; the hypothesis that CMV can be spread through axonal transport, but only in the developing axon, will be tested. The hypothesis that interferons alpha/beta and gamma can reduce or eliminate CMV from the brain will be addressed with in vitro and in vivo experiments. Parallel experiments will test the hypothesis that CMV activates interferon pathways in the mature brain, but not in the developing brain. Mice lacking interferon receptors will be used to test further that CMV effects are mediated by these receptors and not by a non-specific action of CMV. An ultrastructural analysis will assess differential virus binding to immature and mature neurons, and determine where on the neuron surface CMV binds. In the immunocompromised CNS, the olfactory system shows the greatest levels of infection; we will address the hypothesis that the olfactory system is a weak link in the brain's protection against virus in SCID mice. The hypothesis that neurons that recover from CMV still show physiological dysfunction will be tested with whole cell patch clamp recording using current and voltage clamp and with fura-2 calcium digital imaging. CMV can remain latent for long periods. We will test the hypothesis that after interferon or gangciclovir treatment and recovery from infection, CMV can escape from neuronal latency, and establish a new round of productive infectious virus. These experiments will help us understand the mechanisms associated with CMV-induced neurological dysfunction, and how to combat the virus within the brain with minimal complications.